Electrical means for operating fluid pressure indicating gauges and signaling devices



July 18, 1950 R. c. FULLER ELECTRICAL MEANS FOR OPERATING FLUID PRESSURE INDICATING GAUGES AND SIGNALING DEVICES Filed Dec. 14, 1946 2 Sheets-Sheet 1 a k J my Ilia I54 b I fkremor July 18, 1950 R. c. FULLER 2,515,867

ELECTRICAL MEANS FOR OPERATING FLUID PRESSURE INDICATING GAUGES AND SIGNALING DEVICES Filed Dec. 14, 1946 2 Sheets-Sheet 2 Patented July 18, 1950 ELECTRICAL MEANS FOR OPERATING FLUID PRESSURE INDICATING GAUGES AND SIG- NALING DEVICES Reginald Cyril Fuller, Brighton, England Application December 14, 1946, Serial No. 716,208

, In Great Britain December 19, 1945 7 Claims.

This invention relates to an electrically operated switch adapted to respond to the influence of hydraulic or gaseous fluid pressure for automatically making and/or breaking a circuit for apparatus actuated electrically and having a certain operative relationship with the hydraulic or gaseous fluid pressure generating means, or means consuming energy from the source of fluid pressure or converting such pressure into kinetic energy. Or the switch may in one form of the invention be adapted as a means for controlling the operation of a fluid pressure indicating gauge, signalling device or automatic controlling device.

Fluid pressure operated switches have been proposed heretofore in which a diaphragm exposed to the direct influence of the fluid pressure is deformed to actuate contacts Also the use of a stack of carbons in the circuit of pressure gauge indicating apparatus has ben proposed heretofore, in which the variations in resistance in the carbon stack influence the electrical circuit to produce changes in the indications of the gauge. The object of the present invention is to provide a switch which is extremely sensitive in its re sponse to very slight changes in fluid pressure whilst being protected against overload by the fluid pressure and the mechanical means which at an appropriate stage overcomes or yields to the fluid pressure to actuate the switch.

According to this invention a fluid pressure actuated switch comprises engaging contacts to receive leads of a signal operating circuit, at least one of which contacts is a carbon body, spring means and a fixed abutment between which at least one carbon contact is subjected to pressure, a stud slidable through said abutment and having a flanged head at one end, an imperforated flexible diaphragm contacted by said head, the other end of the stud being positioned so as to transmit the load due to the predetermined fluid pressure on the diaphragm to said spring so as to reduce the spring pressure on the contacts, a fluid pressure receiving chamber adapted to be connected to a source of fluid pressure and between which and said abutment said imperforated flexible diaphragm is secured by a continuous peripheral marginal part so that the imperforated diaphragm completely isolates the said chamber from the said stud and contacts, a recess in said abutment accommodating said stud head and of such a depth that slight deformation of the diaphragm under the influence of fluid pressure will result in the said head being stopped against the abutment at substantially the stage when the spring pressure on the contacts is freed or reduced to an extent sufiicient to cause a signal to be transmitted in the circuit, said abutment acting as a positive stop to prevent the spring pressure from being transmitted to the diaphragm to an extent which will subject the diaphragm to deformation greater than the deformation to which it is subjected by the fluid pressure.

In order that the invention may be clearly understood and readily carried into efiect drawings are appended hereto illustrating embodiments thereof, and wherein:

Figure 1 is a plan view, and

Figure 2 is a sectional elevation showing an embodiment of the invention using a single carbon ring,

Figure 3 is a detail broken sectional elevation showing the use of a stack of carbon rings instead of a single carbon ring,

Figure 4 is a detail sectional elevation showing the use of carbon rings alternating with metallic conductor rings and arranged as a stack,

Figures 5 and 6 are detail sectional elevation views showing alternative pairs of the contact elements, and

Figures 7 and 8 are diagrams showing the connection of the device in the electrical circuit of an electrically operated pressure indicator.

Referring to the drawings, the variable electric resistance comprises either a single annular carbon ring I as shown in Figure 2 or a stack of carbon rings la as shown in Figure 3 or as a further alternative, a number of carbon rings lb alternating with metallic conducting rings to as shown in Figure 4. The ring or rings, is or are, enclosed in an insulating tube 2, pressure against a contact plate 3 on top of the carbon ring or rings being applied by an adjustable device comprising a coiled compression spring 4 interposed between the top contact plate 3 and a plate 5 carried by an adjusting screw 6, such screw conveniently comprising a terminal to which can be connected one end of a lead 1 from the gauge or signalling device indicated diagrammatically at 8 in Figure '7.

The said insulating tube forms part of, or is accommodated within a housing, which is partitioned into one end portion provided with an adaptor or union device 9 for the reception of a pipe, or for attachment to the output of a pump, so that the pressure of the circulating system is transmitted directly to a diaphragm [0. This diaphragm can be metallic or composed of a non-porous fabric and is engaged on the side remote from the fluid pressure receiving side by the flanged end of a stud II passing loosely through a bottom contact plate I2 and the carbon ring I or stack of carbon rings Ia or stack of carbon rings and metallic rings, this stud being of insulating material and having a flanged end adjacent to the diaphragm, so that displacement of the diaphragm It due 'to'the pressure of hydraulic fluid causes the insulated stud II to engage with the top contact plate 3 and thus relieves the carbon ring or stack of rings from the pressure due to the action of the said coiled compression ring 4. Relaxation of the spring pressure on the carbon ring I or stack of rings produces a change in resistance whichcan be recorded by a simple type of indicatingmeter 8, or by varying the luminosity of a lamp 13 (see Figure 7), so that the lamp is only illuminated fully when there is no working pressureupon the fluid, or when such pressure drops below a predetermined minimum. Then a gauge is,employed for indicating the pressure in the appropriate fluid pressure circuit it can include a segment divided into a number of distinctively coloured sections indicating changes from maximumpressure to no pressure and so operate from-the device asto be brought successively into view.

When the device is intended for use .in;. connec+ tion with a lubricating circuit of an internal combustion engine, or for like purposes, the dimensions of the housing 2 can be such that it is merely an inconspicuous fitment to the appropriate part of the apparatus, and for normal requirements the housing 2 can comprise the cylindrical body as shown having an annular flange 2a, the diameter of which need not exceed about one and a half inches, the other body part 9 of the device being likewise-flanged as at 9a, the two flanges being coupled together, with the :bottom contact plate I2 and diaphragm it gripped between them by an annular or gland nut L4 threaded onto the flange 9a. In practice the electrical circuit is completed through the carbon ring I or stack of rings, e. g. in the arrange,- ment shown in Figure 3 or i one end ring of the stack is connected electrically to the coil spring via the top contact plate 3 and thereby being electrically connected to the aforesaid pressure adjusting screw 3 and the indicator 8 and the other end carbon ring being connected tothe bottom contact plate I2 which can be fitted with a terminal I20, for connection by a lead I2b to a battery, or may be directly connected vvia the union device 9 to earth. The upper and lower faces of the single carbon ring will take the place of the faces of the rings Ia or Ib which contact with the contact plates 3 and I2.

The device is arranged so that the maximum pressure actually breaks the circuit through the carbon or carbons after increasing the resistance.

When it is required to have the lamp I 3 illuminated when there is a state of high pressurae, g. when the blades of an oil pressure operated adjustable pitch airscrew are feathered, the arrangement shown in Figure 8 can be-adopted in which the warning device I3 can be connected across both leads '5 and I217, and a suitable resistance I introduced in the negative lead so that the warning device is operated when the pressure on the carbon disc or discs is at its highest.

To obviate excessive pressure damaging the diaphragm It, the insulatedstud ,Il abutsagainst the bottom contact-plate l2 thereby-restricting any further movement of the insulated stud and diaphragm after they have performed the function of varying the resistance and finally breaking the circuit at a predetermined pressure.

Instead of connecting the leads I and Ill) to the members 6 and I2, they can, as shown in Figure 5, be connected to diametrically ppposed narrowly spaced part annular brass contact blocks or studs I6 and I1 interposed between a solid carbon disc I and the plate I2, the plates 3 and I 2 being non-conductive, or being insulated ,from the carbon member I and contact members I6 and. Alternatively, as shown in Figure 6, the leads I and I2?) can be connected to a pairofkpartannular or other suitably shaped narrowly spaced carbon bodies Ia and I b interposed between a non-conducting plate I2 and a brass or other suitable conductor disc I8 adapted to act as a bridge across the two carbon bodies, and insulating plate I9 transmitting the pressure of ,thespringtl to the carbon bodies Ia and lb. The disc I 8 will receive the direct pressure :of the stud II.

I claim:

1. A fluid pressure .actuated switch comprising engaging contacts to receive leadsof .a signal operating circuit, at least one of which contacts is a carbon body, spring-means and a fixed abutment between which the carbon portionof the contacts is subjected to pressure, va stud slidable through said abutment and having a flanged head at one end, an imperforated flexible diaphragm contacted by-said head,-the other end of the stud being positioned so as to transmit the load :due to the predetermined fluid pressure on the diaphragm to said spring so as to reduce the spring pressure on the contacts, ;a fluid pressure receiving chamber adapted to be connected to a source of fluid pressure and between which and said abutment said imperforated flexible diaphragm is secured by a continuous peripheral marginal part so that the imperforated diaphragm completely isolates the said chamber from the said stud and contacts, a recess in said abutment accommodating said stud head and of such adepth that slight deformation of the diaphragm under the influence of fluid pressure will .result'in the said head being stopped against the abutment at substantially the stage when the spring pressure on the contacts is freed or reduced to an extent sufii cient to cause a signal to be trammitted in the circuit, said abutment acting as a positive stop to prevent the spring pressure from being transmitted to the diaphragm to an extent which will subject the diaphragm to deformation greater than the deformation to which it is subjected by the fluid pressure.

2. In a switch according to claim 1, the combination with said fixed abutment of another abutment interposed between the spring means and the carbon portion of the contacts, the said stud being slidable through and relative to said fixed abutment and engaging the other abutment so that the spring means yieldingly opposes the hydraulic pressure transmitted to it via said stud.

3. A fluid pressure actuated switch comprising engaging contacts to receive leads of a signal operating circuit, at least one of which contacts is a carbon body, spring means and a fixed abutment between which the carbon portion of the contacts is subjected to pressure, a stud slidable through said abutment and having a flanged head at one end, an imperforated flexible diaphragm contacted by said head, the other ,end of :thestudbcing positioned; so asto transmit the load due to the predetermined fluid pressure on the diaphragm to said spring so as to reduce the spring pressure on the contacts, a fluid pressure receiving chamber adapted to be connected to a source of fluid pressure and between which and said abutment said imperforated flexible diaphragm is secured by a continuous peripheral marginal part so that the imperforated diaphragm completely isolates the said chamber from the said stud and contacts, a recessin said abutment accommodating said stud head and of such a depth that slight deformation of the diaphragm under the influence of fluid pressure will result in the said head being stopped against the abutment at substantially the stage when the spring an extent sufilcient to cause a signal tobe transmitted in the circuit, said abutment acting as a positive stop to prevent the spring pressure from being transmitted to the diaphragm to an extent which will subject the diaphragm to deformation greater than the deformation to which it is subjected by the fluid pressure, a second abutment interposed between a spring means and a carbon portion of the contacts, the said stud being slidable through and relative to said fixed abutment and engaging the second abutment so that the spring means yieldingly oppose the hydraulic pressure transmitted thereto through said stud, the stem or shank of the headed stud passing freely through a carbon contact body of annular form.

4. A switch according to claim 3, wherein the carbon body is divided into a plurality of carbon elements arranged as a stack.

5. A switch according to claim 3, wherein the pressure on the contacts is freed or reduced to V REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 805,505 Waddell Nov. 28, 1905 1,528,627 Peters Mar. 3, 1925 1,581,957 Keller Apr. 20, 1926 1,681,314 Vawter Aug. 21, 1928 1,695,295 Rollins Dec. 18, 1928 1,788,678 Knaak Jan. 13, 1931 1,796,919 Brogger Mar. 17, 1931 2,030,523 Keller Feb. 11, 1936 2,163,518 Postelwaite June 20, 1939 2,347,695 Leathers May 2, 1944 FOREIGN PATENTS Number Country Date 471,422 Great Britain Sept. 3, 1937 705,669 France June 11, 1931 

